1. Field of the Invention
The present invention relates to a spacer element for guiding flowing medium, especially for apparatus for filtering and separating the flowing medium by microfiltration, ultrafiltration, and reverse osmosis, with a respective filter element being accommodated between each two essentially plate-like spacer elements, about which the flowing medium flows.
2. Description of the Prior Art
A multi-part device for accommodating filter elements is known, for example, from the apparatus for separating and filtering flowing medium disclosed in German Offenlegungsschrift 33 27 431, where each individual filter unit of any desired number of filter element stacks comprises a carrier plate, a deflector plate, and accommodated therebetween, a diaphragm. With this known apparatus, the periphery of the diaphragm is adhesively joined to the periphery of the carrier plate within an axial passage.
Such a known compact construction of filter units to form a filter element stack is known as a so-called disk module. As a consequence of the individual filter units, the disks or plates have a relatively great inherent stability and must be provided with a relatively high pressure resistance since the type of diaphragm filter used there absolutely demands this.
Due to the construction of the heretofore known spacer elements and of the apparatus in which these known spacer elements are inserted, a considerable partial pressure drop occurs between the inlet (unfinished solution, i.e. solution that is only partially treated or not treated at all) and the outlet (retentate) of the flowing medium into and out of the apparatus since the flowing medium of these apparatus generally flow through from the inlet to the outlet in a series-type arrangement and in a meander-like way along the diaphragm filters that are held by the spacer elements or disks. An important reason for the considerable partial pressure drop, which generally has a disadvantageous effect, is that the diaphragm rests directly upon the carrier plate and/or upon the deflector plate, so that the flowing medium becomes increasingly obstructed as it flows through the filter element stack.
For certain applications, for such apparatus neither the known spacer elements, which are formed of carrier plates and deflector plates upon which up to now the diaphragm rests, nor the up to now conventionally used diaphragms, are suitable.
An apparatus is also known (German Offenlegungsschrift 33 47 283) where so-called diaphragm cushions or pads are used that comprise two outer thin diaphragm sheets that are hermetically sealed relative to flowing medium along their outer edges, and where the filtrate flows to a hole that is provided in the diaphragm pad and that, for example, is disposed essentially centrally therein, although this is not absolutely necessary, and from where the filtrate is suitably collected and supplied to a filtrate outlet.
The apparatus that have been known up to now and that have used conventional diaphragms are not suitable for cooperation with the aforementioned diaphragm pads, since with such pads it is not possible for the medium to flow on both sides of the diaphragm pad in order to fully utilize the advantages of the symmetrically constructed diaphragm pad. Tests have been conducted in which the diaphragm pad has been placed upon a carrier plate or deflector plate via the interposition of a spacer that is comprised of gauze or fabric. However, by using this measure the filter effect of one active surface of the diaphragm is practically not utilized, resulting in a considerable reduction in efficiency or non-utilization of the otherwise good separating capacity of such diaphragm pads.
It an object of the present invention to provide a spacer element that permits a good circulation of medium about the filter element, which is disposed on the spacer element and is in the form of a diaphragm pad, so that it is also possible to have a parallel arrangement of diaphragm pads in an apparatus and/or the series arrangement of several units of diaphragm pads arranged in parallel, in order to minimize the pressure drop of the flowing medium between the inlet and the outlet, whereby the diaphragm pads are to be accommodated in a manner that is essentially resistant to pressure differentials.